The invention relates to a filtration membrane, e.g., adapted for use in hemofiltration. The invention also relates to a process for producing such a membrane.
Hemofiltration membranes are well known in the art. For example, in Walch et al. U.S. Pat. No. 4,229,291 there is described a polyamide hemofiltration membrane as well as a process for producing the membrane. A similar membrane is described also in German Patent Publication No. DE-AS 22 36 226. Hemofiltration membranees made of polymers other than polyamide are also known and commercially available. Examples are membranes made of cellulose nitrate (Sartorius; Daicel), polyacrylonitrile (Asahi PAN 15; Rhone-Poulenc AN 69), polysulfone (Amicon), and polyether-polycarbonate block copolymer (European Patent Application No. 80105185.5).
A common drawback of these known membranes is their relatively low ultrafiltration rates (permeabilities to water). To compensate for these low ultrafiltration rates, relatively large membrane surface areas are used to obtain at least a minimal required liquid flow-through when the membranes are used in, for example, hemofiltration. Since the minimal required liquid flow-through is even higher in the filtration of infusion solutions, an even larger membrane surface area must therefore be used to compensate. To illustrate this, a known filtration membrane according to either of U.S. Pat. No. 4,229,291 or German Patent Publication No. DE-AS 22 36 226 (which have ultrafiltration rates of 10-20.times.10.sup.-4 ml/sec..times.cm.sup.2 .times.bar and 10-30.times.10.sup.-4 ml/sec..times.cm.sup.2 .times.bar, respectively) will need an available membrane surface area of at least 0.5-1 m.sup.2 to be able to filtrate the required 100-200 ml/min. of infusion solution at a transmembrane pressure of 100-300 mm.Hg.